Systems for testing the weathering and lightfastness of products such as fabric samples, painted panels, and plastics are presently available, being sold for example by the Atlas Electric Devices Company of Chicago, Ill. See also Suga U.S. Pat. No. 4,627,287 and Huber et al. U.S. Pat. No. 4,843,893 for examples of such testing devices. The above devices test the weathering and lightfastness properties of materials and products under closely controlled conditions.
In the natural environment, heat, light, and moisture combine synergistically to cause optical, mechanical, and chemical changes in products which are exposed to outdoor weathering conditions. Typically, the testing apparatus of this invention and the prior art can be used to obtain such weathering data on an accelerated time basis, to permit product manufacturers to gain information as to how their products will stand up to weathering over the months or years.
As shown in the previously cited patents, a weathering testing apparatus may use air which circulates through the system to control the temperature of samples being tested so that they are not overheated by the radiation source, which typically may be a high intensity plasma lamp such as a xenon lamp. In both of the above patents, air from a pump is directed by means of a conical baffle in desired flow directions for flowing across the samples.
In accordance with this invention, improvements to weathering testing systems are provided. The samples being tested may be uniformly air cooled, with an air flow pattern which is different from, and having significant advantages over, the air flow patterns of the prior art patents cited above. Highly uniform air flow is provided, with good cooling efficiency so that a lower power air pump may operate at a lower speed of operation for savings of power, lengthening of the useful life of the air pump, and with the use of a lower capacity, lower cost pump.
Also, the high intensity plasma lamp which is used is desirably positioned in a highly uniform way so that the light emitted by the lamp remains entirely constant. However, the plasma lamp is removed from its fitting on occasion. When this is done, it is desirable for the plasma lamp to be replaced again in exactly the same rotational position as before, so that the light pattern remains constant. This is especially important when using a calibrated plasma lamp to calibrate the light monitor system.
Additionally, it is important for the high intensity plasma lamp to be precisely positioned in a central, coaxial position relative to the rack upon which the samples for testing are attached. By this invention, an adjustable fitting is provided which permits small adjustments of the plasma lamp so that it may be properly aligned and positioned.
Additionally, in the prior art, it is known to monitor the ignition of a high intensity plasma lamp in a weathering testing system by providing an electrical current flow sensing system such as an ammeter to the apparatus. By this invention, a different technique of monitoring the lighting of the lamp may be used, so that the need for the ammeter is dispensed with. In typical weathering testing apparatus, there is no need for any added hardware to replace the current flow sensing system, apart from a software program which may be installed in the microprocessor, which may be already present for other control functions.